Low temperature sintered ceramic capacitor having a high resistivity and bending strength, and method of manufacture

ABSTRACT

A monolithic capacitor having a dielectric ceramic body cosintered with at least two base metal electrodes buried therein. The ceramic body is composed of a major ingredient expressed by the formula, 
     
         (Ba.sub.1-v-w Me.sub.v Mg.sub.w O).sub.k (Zr.sub.1-x-y Ti.sub.x 
    
      Si y )O 2   
     where Me is either or both of strontium and calcium, and v, w, x, y and k are numerals in specified ranges. To this major ingredient is added a minor proportion of a mixture of boric oxide, silicon dioxide, and one or more metal oxides selected from among barium oxide, magnesium oxide, zinc oxide, strontium oxide and calcium oxide. For the fabrication of capacitors the mixture of the above major ingredient and additives in finely divided form are formed into moldings of desired shape and size, each with at least two electrodes buried therein. The moldings and electrodes are cosintered in a reductive or neutral atmosphere at temperatures of less than 1200° C., and then are reheated at a lower temperature in an oxidative atmosphere.

BACKGROUND OF THE INVENTION

Our invention relates to solid dielectric capacitors and moreparticularly to ceramic capacitors of the monolithic type which arecapable of manufacture by cosintering of the ceramic body and theelectrodes at such low temperatures as to permit use of a base metal asthe electrode material. Our invention also specifically pertains to aprocess for the fabrication of such ceramic capacitors.

Multilayered ceramic capacitors have long been known and usedextensively which employ noble metals such as platinum and palladium asthe electrode materials. Generally, for the manufacture of suchcapacitors, there are first prepared "green" (unsintered) dielectricsheets from the proportioned ingredients of a desired dielectric ceramicmaterial in finely divided form. An electroconductive paste containingpowdered platinum or palladium is then "printed" on the green sheets ina desired pattern. A plurality of such printed green sheets are stackedup, pressed together, and sintered in a temperature range of 1300° to1600° C. in an oxidative atmosphere.

This conventional method makes possible the simultaneous firing(cosintering) of the dielectric ceramic layers and the film electrodesinterleaved therewith. It is also an acknowledged advantage of the knownmethod that the noble metal electrodes are totally unaffected by thehigh temperature sintering in an oxidative atmosphere. Offsetting allthese advantages is the expensiveness of the noble metals, which addconsiderably to the costs of the multilayered ceramic capacitors.

Japanese Laid Open Patent Application No. 53-98099 suggests a solutionto the above discussed problem, teaching ceramic compositions consistingprimarily of calcium zirconate (CaZrO₃) and manganese dioxide (MnO₂). Inthe manufacture of ceramic capacitors the dielectric bodies of theseknown compositions are sinterable in a reductive atmosphere, so thatelectrodes of nickel or like base metal can be employed for cosinteringwith the dielectric bodies without the danger of oxidation.

We do, however, object to the prior art CaZrO₃ -MnO₂ ceramiccompositions for several reasons. These known ceramic compositionsrequire firing in as high a temperature range as from 1350° to 1380° C.When the green sheets of the ceramic compositions, having printedthereon a paste composed primarily of powdered nickel, are sintered inthat temperature range, the nickel particles tend to grow and flocculatein spite of the nonoxidative atmosphere in which they are fired. We havealso found that the base metal particles are easy to diffuse into theceramic bodies when fired in that temperature range. The flocculationand diffusion of the base metal particles are, of course, bothundesirable as the resulting capacitors will in all likelihood fail topossess desired values of capacitance and insulation resistance.

These weaknesses of the CaZrO₃ -MnO₂ ceramic compositions have beenovercome to some extent by Kishi et al. U.S. Pat. Nos. 4,700,265 and4,709,299, both teaching dielectric ceramic compositions that permitcosintering at temperatures of not more than 1200° C. The compositionsaccording to U.S. Pat. No. 4,700,265 consist essentially of a majoringredient expressed by the general formula, (SrO)_(k) (Zr_(1-x) Ti₂)O₂,and minor proportions of lithium oxide (Li₂ O), silicon dioxide (SiO₂),and at least one metal oxide selected from among barium oxide (BaO),magnesium oxide (MgO), zinc oxide (ZnO), strontium oxide (SrO) andcalcium oxide (CaO). U.S. Pat. No. 4,709,299, on the other hand,proposes compositions consisting essentially of a major ingredientexpressed by the general formula, (CaO)_(k) (Zr_(1-x) Ti_(x))O₂, andminor proportions of boric oxide (B₂ O₃), SiO₂, and at least one metaloxide selected from among BaO, MgO, ZnO, SrO and CaO. compositionsaccording to U.S. Pat. No. 4,700,265.

The ceramic compositions suggested by the noted U.S. patents permitcosintering of the dielectric bodies and base metal electrodes in areductive or neutral atmosphere at temperatures not exceeding 1200° C.Little or no flocculation of the base metal, particularly nickel, takesplace because of the low sintering temperatures. The resulting ceramiccapacitors are particularly well suited for temperature compensatingapplications, having a specific dielectric constant of not less than 30,a temperature coefficient of capacitance of -800 to +140 parts permillion (ppm) per degree centigrade (C.), a Q factor of not less than2000, a resistivity of not less than 1×10⁷ megohm-centimeters(megohm-cm), and a bending strength of approximately 1300 kilograms persquare centimeter (kg/cm²).

While these performance characteristics of the closest prior art aresatisfactory for all practical purposes, we have nevetheless been hardpressed by our customers for dielectric ceramics of higher performancecharacteristics. For example, an improvement in resistivity will resultin capacitors of greater voltage withstanding capability. An improvementin bending strength will result in less breakage of capacitors duringtheir manufacture and mechanical mounting on circuit boards. Animprovement in specific dielectric constant will result in capacitors ofhigher capacitance or, if the capacitance is maintained the same asheretofore, in capacitors of greater interelectrode spacing. The greaterinterelectrode spacing is desirable from the standpoint of less voltageper unit thickness of the ceramic body.

SUMMARY OF THE INVENTION

We have hereby invented how to improve the performance characteristics,notably the resistivity and bending strength, of the ceramic capacitorsof the class under consideration without loss or diminution of theconventionally gained advantage of cosinterability at temperatures of nomore than 1200° C. in a reductive or neutral atmosphere.

Briefly summarized in one aspect thereof, our invention provides a lowtemperature sintered solid dielectric capacitor of improved performancecharacteristics, comprising a dielectric ceramic body and at least twoelectrodes in contact therewith. The dielectric ceramic body consistsessentially of: (a) 100 parts by weight of a major ingredient expressedby the general formula, (Ba_(1-v-w) Me_(v) Mg_(w) O)_(k) (Zr_(1-x-y)Ti_(x) Si_(y))O₂, where Me is at least either of strontium (Sr) andcalcium (Ca), v a numeral in the range of 0.005-0.980, w a numeral inthe range of 0.001-0.050, x a numeral in the range of 0.00-0.50, y anumeral in the range of 0.005-0.100, and k a numeral in the range of0.80-1.25; and (b) from 0.2 to 10.0 parts by weight of an additivemixture of B₂ O₃, SiO₂ and at least one of BaO, MgO, ZnO, SrO and CaO.The relative proportions of B₂ O₃, SiO₂ and at least one selected metaloxide, altogether constituting the additive mixture, will be specifiedin conjunction with the ternary diagram attached hereto.

The ceramic capacitor of our invention, having its dielectric bodyformulated as set forth in the foregoing, has proved to have varyfavorable performance characteristics. The test capacitors manufacturedin accordance with our invention, to be disclosed in detailsubsequently, had resistivities of not less than 1×10⁸ megohm-cm,bending strengths of not less than 1500 kg/cm, specific dielectricconstants of not less than 35, temperature coefficients of capacitanceof -1000 to +45 ppm per degree C., and Q factors at 1 megahertz (MHz) ofnot less then 5000.

Another aspect of our invention concerns a method of fabricating theabove outlined ceramic capacitor. The method dictates, first of all, thepreparation of a mixture of the major ingredient and the additives infinely divided form. This mixture is then molded into a body of desiredshape and size, which is provided with at least two electrode portionsof an electroconductive material in any convenient manner. Then themolding with the electrode portions is sintered in a nonoxidative (i.e.reductive or neutral) atmosphere and is subsequently reheated in anoxidative atmosphere.

We recommend a temperature range of 1050° to 1200° C. for sintering thedielectric molding. This temperature range is sufficiently low to permitthe cosintering, in a reductive or neutral atmosphere, of nickel or likebase metal electrodes on the dielectric molding without the likelihoodof the flocculation or diffusion of the base metal.

The above and other features and advantages of our invention and themanner of realizing them will become more apparent, and the inventionitself will best be understood, from a study of the followingdescription and appended claims taken together with the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional representation of a monolithic, multilayeredceramic capacitor capable of manufacture in accordance with ourinvention, the illustrated capacitor being representative of numeroustest capacitors fabricated in the Examples of our invention to bepresented subsequently;

FIG. 2 is a diagrammatic illustration of apparatus used for measuringthe bending strength of the test capacitors; and

FIG. 3 is a ternary diagram depicting the relative proportions of theadditives of the ceramic compositions in accordance with our invention.

DETAILED DESCRIPTION

We have illustrated in FIG. 1 one of many monolithic ceramic capacitorsof like construction fabricated in the subsequent Examples of ourinvention by way of a preferable embodiment thereof. Generallydesignated 10, the respresentative capacitor is shown to have aninterlamination of three dielectric ceramic layers 12 and two filmelectrodes 14. The three ceramic layers 12 constitute in combination asolid dielectric body 15 having the low temperature sintered ceramiccompositions in accordance with our invention. The two film electrodes14, which can be of a low cost base metal such as nickel, extend fromthe opposite sides of the dielectric body 15 toward, and terminate shortof, the other sides of the dielectric body and so have an overlapping,parallel spaced relation to each other. A pair of conductiveterminations 16 contact the respective film electrodes 14. Eachtermination 16 is shown to comprise a baked on zinc layer 18, a platedon copper layer 20, and a plated on solder layer 22.

Typically, and as fabricated in the subsequent Examples of ourinvention, the intermediate one of the three dielectric layers 12 has athickness of 0.02 millimeter (mm). The area of that part of each filmelectrode 14 which overlaps the other film electrode is 25 mm² (5×5 mm).

EXAMPLES

We fabricated 98 different sets of test capacitors, each constructed asin FIG. 1, some having their dielectric bodies formulated in accordancewith the ceramic compositions of our invention and others not, andmeasured their specific dielectric constant, temperature coefficient ofcapacitance, Q factor, resistivity, and bending strength. Table 1 liststhe compositions of the dielectric bodies of all the test capacitorsfabricated.

The major ingredient of the ceramic compositions in accordance with ourinvention has been herein defined as (Ba_(1-v-w) Me_(v) Mg_(w) O)_(k)(Zr_(1-x-y) Ti_(x) Si_(y))O₂, where Me is either or both of Sr and Ca.Accordingly, in Table 1, we have given various combinations of theatomic numbers k, v, w, x and y in the formula to indicate the specificmajor ingredients employed in the various Tests. The ceramiccompositions of our invention further include mixtures, in variousproportions, of additives B₂ O₃, SiO₂ and MO. Table 1 specifies theamounts, in parts by weight, of the additive mixtures with respect to100 parts by weight of the major ingredients, as well as the relativeproportions, in mole percent, of the additives B₂ O₃, SiO₂ and MO.Further, since MO can be any one or more of BaO, MgO, ZnO, SrO and CaO,Table 1 gives the relative proportions, in mole percent, of these metaloxides.

                                      TABLE 1                                     __________________________________________________________________________    Ceramic Compositions                                                                                  Additives                                             Major Ingredient (100 wt. parts)                                                                            Composition                                     Test   -v               Amount                                                                              (mole %) MO (mole %)                            No.                                                                               -k                                                                              Sr Ca Sum                                                                               .sub.--w                                                                         -x                                                                               -y                                                                              (wt. parts)                                                                         B.sub.2 O.sub.3                                                                  SiO.sub.2                                                                        MO BaO                                                                              MgO                                                                              ZnO                                                                              SrO                                                                              CaO                        __________________________________________________________________________     1 1.00                                                                             0.100                                                                            0.100                                                                            0.200                                                                            0.010                                                                            0.20                                                                             0.010                                                                            1.0    1 80 19 20 20 20 20 20                          2 "  "  "  "  "  "  "  "      1 39 60 "  "  "  "  "                           3 "  "  "  "  "  "  "  "     29  1 70 "  "  "  "  "                           4 "  "  "  "  "  "  "  "     90  1  9 "  "  "  "  "                           5 "  "  "  "  "  "  "  "     "   9  1 "  "  "  "  "                           6 "  "  "  "  "  "  "  "     19 80 "  "  "  "  "  "                           7 "  "  "  "  "  "  "  "     10 85  5 "  "  "  "  "                           8 "  "  "  "  "  "  "  "      5 30 65 "  "  "  "  "                           9 "  "  "  "  "  "  "  "     "  20 75 "  "  "  "  "                          10 "  "  "  "  "  "  "  "     15 10 75 "  "  "  "  "                          11 "  "  "  "  "  "  "  "     10  5 85 "  "  "  "  "                          12 "  "  "  "  "  "  "  "     95  0  5 "  "  "  "  "                          13 "  "  "  "  "  "  "  "     10 80 10 "  "  "  "  "                          14 "  "  "  "  "  "  "  "      5 65 30 "  "  "  "  "                          15 "  "  "  "  "  "  "  "     "  45 50 "  "  "  "  "                          16 "  "  "  "  "  "  "  "     10 30 60 "  "  "  "  "                          17 "  "  "  "  "  "  "  "     25 15 "  "  "  "  "  "                          18 "  "  "  "  "  "  "  "     40  5 55 "  "  "  "  "                          19 "  "  "  "  "  "  "  "     60 10 30 "  "  "  "  "                          20 "  "  "  "  "  "  "  "     80 15  5 "  "  "  "  "                          21 "  "  "  "  "  "  "  "     50 45  5 "  "  "  "  "                          22 "  "  "  "  "  "  "  "     30 35 35 100                                                                              -- -- -- --                         23 "  "  "  "  "  "  "  "     "  "  "  -- 100                                                                              -- -- --                         24 "  "  "  "  "  "  "  "     "  "  "  -- -- 100                                                                              -- --                         25 "  "  "  "  "  "  "  "     "  "  "  -- -- -- 100                                                                              --                         26 "  "  "  "  "  "  "  "     "  "  "  -- -- -- -- 100                        27 "  "  "  "  "  "  "  "     "  "  "  20 20 20 20 20                         28 "  "  "  "  "  "  "  "     "  "  "  10 10 40 20 20                         29 "  "  "  "  "  "  "  "     "  "  "  30 10 20 10 30                         30 "  "  "  "  "  "  "  "     "  "  "  20 30 -- 20 30                         31 "  "  "  "  "  "  "  "     "  "  "  10 20 30 30 10                         32 "  "  "  "  "  "  "  "     "  "  "  20 10 10 "  30                         33 1.01                                                                             0  -- 0  0.005                                                                            0.10                                                                             0.010                                                                            "     15 75 10 20 20 20 20 20                         34 "  0.010                                                                            -- 0.010                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          35 "  0.010                                                                            -- 0.010                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          36 "  0.500                                                                            -- 0.500                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          37 "  0.980                                                                            -- 0.980                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          38 "  0.995                                                                            -- 0.995                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          39 0.99                                                                             -- 0  0  "  "  "  "     20 60 20 "  "  "  "  "                          40 "  -- 0.005                                                                            0.005                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          41 "  -- 0.200                                                                            0.200                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          42 "  -- 0.700                                                                            0.700                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          43 "  -- 0.900                                                                            0.900                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          44 "  -- 0.995                                                                            0.995                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          45 1.00                                                                             0  0  0  "  "  "  "     14 45 40 "  "  "  "  "                          46 "  0.010                                                                            0.010                                                                            0.020                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          47 "  0.100                                                                            0.300                                                                            0.400                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          48 "  0.600                                                                            0.200                                                                            0.800                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          49 "  0.400                                                                            0.500                                                                            0.900                                                                            "  "  0.001                                                                            "     "  "  "  "  "  "  "  "                          50 "  0.500                                                                            0.495                                                                            0.995                                                                            "  "  "  "     "  "  "  "  "  "  "  "                          51 0.95                                                                             0.200                                                                            0.100                                                                            0.300                                                                            0  0.05                                                                             0.200                                                                            2.0   25 25 50 "  "  "  "  "                          52 "  "  "  "  0.002                                                                            "  "  "     "  "  "  "  "  "  "  "                          53 "  "  "  "  0.005                                                                            "  "  "     "  "  "  "  "  "  "  "                          54 "  "  "  "  0.010                                                                            "  "  "     "  "  "  "  "  "  "  "                          55 "  "  "  "  0.030                                                                            "  "  "     "  "  "  "  "  "  "  "                          56 "  "  "  "  0.050                                                                            "  "  "     "  "  "  "  "  "  "  "                          57 "  "  "  "  0.060                                                                            "  "  "     "  "  "  "  "  "  "  "                          58 1.10                                                                             0.300                                                                            0.400                                                                            0.700                                                                            0  0.37                                                                             0.005                                                                            3.0   40 "  35 "  "  "  "  "                          59 "  "  "  "  0.001                                                                            "  "  "     "  "  "  "  "  "  "  "                          60 "  "  "  "  0.020                                                                            "  "  "     "  "  "  "  "  "  "  "                          61 "  "  "  "  0.040                                                                            "  "  "     "  "  "  "  "  "  "  "                          62 "  "  "  "  0.050                                                                            "  "  "     "  "  "  "  "  "  "  "                          63 "  "  "  "  0.060                                                                            "  "  "     "  "  "  "  "  "  "  "                          64 0.98                                                                             0.200                                                                            0.100                                                                            0.300                                                                            0.030                                                                            0  0.020                                                                            2.0   55 30 15 "  "  "  "  "                          65 "  "  "  "  "  0.01                                                                             "  "     "  "  "  "  "  "  "  "                          66 "  "  "  "  "  0.10                                                                             "  "     "  "  "  "  "  "  "  "                          67 "  "  "  "  "  0.30                                                                             "  "     "  "  "  "  "  "  "  "                          68 "  "  "  "  "  0.50                                                                             "  "     "  "  "  "  "  "  "  "                          69 "  "  "  "  "  0.55                                                                             "  "     "  "  "  "  "  "  "  "                          70 1.03                                                                             0  1.000                                                                            1.000                                                                            0  0.05                                                                             0  2.0   35 55 10 "  "  "  "  "                          71 "  0.050                                                                            0.050                                                                            0.100                                                                            0.020                                                                            "  "  "     "  "  "  "  "  "  "  "                          72 "  "  "  "  "  "  0.005                                                                            "     "  "  "  "  "  "  "  "                          73 "  "  "  "  "  "  0.030                                                                            "     "  "  "  "  "  "  "  "                          74 "  "  "  "  "  "  0.100                                                                            "     "  "  "  "  "  "  "  "                          75 "  "  "  "  "  "  0.110                                                                            "     "  "  "  "  "  "  "  "                          76 0.79                                                                             0.200                                                                            0.200                                                                            0.400                                                                            0.030                                                                            0.25                                                                             0.020                                                                            1.0   30 45 25 "  "  "  "  "                          77 0.80                                                                             "  "  "  "  "  "  "     "  "  "  "  "  "  "  "                          78 0.90                                                                             "  "  "  "  "  "  "     "  "  "  "  "  "  "  "                          79 1.00                                                                             "  "  "  "  "  "  "     "  "  "  "  "  "  "  "                          80 1.10                                                                             "  "  "  "  "  "  "     "  "  "  "  "  "  "  "                          81 1.20                                                                             "  "  "  "  "  "  "     "  "  "  "  "  "  "  "                          82 1.25                                                                             "  "  "  "  "  "  "     "  "  "  "  "  "  "  "                          83 1.26                                                                             "  "  "  "  "  "  "     "  "  "  "  "  "  "  "                          84 1.00                                                                             0.100                                                                            0.100                                                                            0.200                                                                            0.015                                                                            0.30                                                                             0.010                                                                            0     15 55 30 "  "  "  "  "                          85 "  "  "  "  "  "  "  0.2   "  "  "  "  "  "  "  "                          86 "  "  "  "  "  "  "  1.0   "  "  "  "  "  "  "  "                          87 "  "  "  "  "  "  "  5.0   "  "  "  "  "  "  "  "                          88 "  "  "  "  "  "  "  10.0  "  "  "  "  "  "  "  "                          89 "  "  "  "  "  "  "  12.0  "  "  "  "  "  "  "  "                          90 1.05                                                                             0.935                                                                            -- 0.935                                                                            0.010                                                                            0.15                                                                             0.100                                                                            1.0    5 50 45 "  "  "  "  "                          91 "  -- 0.935                                                                            "  0.030                                                                            "  "  "     "  "  "  "  "  "  "  "                          92 "  0.400                                                                            0.535                                                                            "  0.040                                                                            "  "  "     "  "  "  "  "  "  "  "                          93 "  "  "  "  0.050                                                                            "  "  "     "  "  "  "  "  "  "  "                          94 "  "  "  "  0.055                                                                            "  "  "     "  "  "  "  "  "  "  "                          95 1.00                                                                             0.620                                                                            0.380                                                                            1.000                                                                            0  0.95                                                                             0  2.0   15 25 60 "  "  "  "  "                          96 "  0.400                                                                            0.300                                                                            0.700                                                                            0.010                                                                            0.50                                                                             0.010                                                                            "     "  "  "  "  "  "  "  "                          97 "  1.00                                                                             0  1.000                                                                            0  0.05                                                                             0  3.0   10 30 "  "  30  0 "  30                         98 "  0.700                                                                            0.050                                                                            0.750                                                                            0.020                                                                            0.05                                                                             0.010                                                                            "     "  "  "  "  "  "  "  "                          __________________________________________________________________________

According to Table 1, the major ingredient of the dielectric bodies ofthe capacitors of Test No. 1 was:

    (Ba.sub.0.79 Me.sub.0.2 Mg.sub.0.01 O).sub.1.0 (Zr.sub.0.79 Ti.sub.0.2 Si.sub.0.01)O.sub.2

or, more specifically, since Me₀.2 was Sr₀.1 Ca₀.1,

    (Ba.sub.0.79 Sr.sub.0.1 Ca.sub.0.1 Mg.sub.0.01 O).sub.1.0 (Zr.sub.0.79 Ti.sub.0.2 Si.sub.0.01)O.sub.2.

One hundred parts of this major ingredient was admixed with 1.0 part byweight of a mixture of one mole percent B₂ O₃, 80 mole percent SiO₂ and19 mole percent MO. MO was a mixture of 20 mole percent BaO, 20 molepercent MgO, 20 mole percent ZnO, 20 mole percent SrO and 20 molepercent CaO.

For the fabrication of the capacitors of Test No. 1 we started with thepreparation of the major ingredient of their dielectric bodies. Weprepared the following start materials for the major ingredient:

Barium carbonate (BaCO₃)

527.70 grams (0.79 mole part)

Strontium carbonate (SrCO₃)

49.97 grams (0.10 mole part)

Calcium carbonate (CaCO₃)

33.85 grams (0.10 mole part)

Magnesium carbonate (MgCO₃)

2.85 grams (0.01 mole part)

Zirconium oxide (ZrO₂)

329.50 grams (0.79 mole part)

Titanium oxide (TiO₂)

54.09 grams (0.20 mole part)

Silica (SiO₂)

2.04 grams (0.01 mole part)

These start materials had all purities of not less than 99.0 percent.The above specified weights of the start materials do not include thoseof the impurities contained. We charged the start materials into a potmill together with alumina balls and 2.5 liters of water and mixed themtogether for 15 hours. Then the mixture was introduced into a stainlesssteel vat and therein dried by air heated to 150° C. for four hours.Then the dried mixture was crushed into relatively coarse particles,which were subsequently fired in air within a tunnel furnace at 1200° C.for two hours. There was thus obtained the major ingredient of the abovespecified composition in finely divided form.

For the provision of the additives of Test No. 1 we prepared:

B₂ O₃ . . . 0.99 grams (1.0 mole percent)

SiO₂ . . . 68.38 grams (80.00 mole percent)

BaCO₃ . . . 10.67 grams (3.8 mole percent)

MgO . . . 2.18 grams (3.8 mole percent)

ZnO . . . 4.40 grams (3.8 mole percent)

SrCO₃ . . . 7.98 grams (3.8 mole percent)

CaCO₃ . . . 5.41 grams (3.8 mole percent)

To these substances we added 300 cubic centimeters of alcohol andstirred the resulting slurry for 10 hours in a polyethylene pot withalumina balls. Then the mixture was air fired at 1000° C. for two hours.Then, charged into an alumina pot together with 300 cubic centimeters ofwater, the fired mixture was pulverized with alumina balls over a periodof 15 hours. Then the pulverized mixture was dried at 150° C. for fourhours. There was thus obtained in finely divided form the desiredadditive mixture of one mole percent B₂ O₃, 80 mole percent SiO₂ and 19mole percent MO, with the MO consisting of 3.8 mole percent BaO, 3.8mole percent MgO, 3.8 mole percent ZnO, 3.8 mole percent SrO and 3.8mole percent CaO.

Ten grams (one weight part) of this additive mixture was added to 1000grams (100 weight parts) of the above prepared major ingredient.Further, to this mixture, we added 15 percent by weight of an organicbinder and 50 percent by weight of water with respect to the totalweight of the major ingredient and additives. The organic binder was anaqueous solution of acrylic ester polymer, glycerine, and condensedphosphate. The mixture of all these was ball milled into a slurry. Thenthis slurry was defoamed in vacuum.

Then we charged the defoamed slurry into a reverse roll coater andshaped it into a thin, continuous strip on an elongate supporting stripof polyester film. Then the strip was dried by heating to 100° C. on thesupporting film. The green ceramic strip thus obtained, approximately 25microns thick, was subsequently punched into "squares" sized 10 by 10centimeters. These green ceramic squares are to become the ceramiclayers 12, FIG. 1, in the completed test capacitors 10.

For the fabrication of the base metal film electrodes 14 on the ceramiclayers 12, we prepared 10 grams of nickel in finely divided form, withan average particle size of 1.5 microns, and a solution of 0.9 gram ofethyl cellulose in 9.1 grams of butyl "Carbitol" (trademark fordiethylene glycol monobutyl ether). Both were intimately intermingled bybeing agitated for 10 hours, thereby providing an electroconductivepaste. Then this paste was "printed" on one surface of each greenceramic square, which had been prepared as above described, through ascreen having 50 perforations of rectangular shape, each sized seven by14 millimeters.

After drying the printed paste, we stacked two green squares, with theirprintings directed upwardly, and with the printings on the two squaresoffset from each other to an extent approximately half the pitch oftheir patterns in the longitudinal direction. The thus stacked twoprinted squares were placed between two separate stacks of fourunprinted squares esch with a thickness of 60 microns. The resultingstack of printed and unprinted squares were pressed in their thicknessdirection under a pressure of approximately 40 tons at 50° C., therebyfirmly bonding the stacked squares to one another. Then the bondedsquares were cut in a latticed pattern into 50 laminate chips ofidentical construction.

We employed a furnace capable of atmosphere control for cofiring theabove prepared green dielectric bodies and, buried therein, theconductive layers which were to become the film electrodes 14 in thecompleted capacitors 10. The chips were first air heated in this furnaceto 600° C. at a rate of 100° C. per hour, thereby driving off theorganic binder that had been used for providing the slurry of thepowdered major ingredient and additives. Then the furnace atmosphere waschanged from air to a reductive (nonoxidative) atmosphere consisting oftwo percent by volume of molecular hydrogen and 98 percent by volume ofmolecular nitrogen. In this reductive atmosphere the furnace temperaturewas raised from 600° C. to 1170° C. at a rate of 100° C. per hour. Themaximum temperature of 1170° C., at which the ceramic bodies formulatedin accordance with our invention were to be sintered to maturity, wasmaintained for three hours. Then the furnace temperature was lowered to600° C. at a rate of 100° C. per hour. Then, with the furnace atmosphereagain changed to air (oxidative atmosphere), the temperature of 600° C.was maintained for 30 minutes for the oxidizing heat treatment of thesintered chips. Then the furnace temperature was allowed to drop to roomtemperature.

Thus we obtained the dielectric ceramic bodies 15, FIG. 1, cosinteredwith the film electrodes 14 buried therein.

We proceeded to the production of the air of conductive terminations 16on both sides of each ceramic body 15 through which were exposed thefilm electrodes 14. First, for the production of the inmost zinc layers18, a conductive paste composed of zinc, glass frit and vehicle wascoated on both sides of each ceramic body 15. The coatings on dryingwere air heated to 550° C. and maintained at that temperature for 15minutes, thereby completing the zinc layers 18 each in direct contactwith one of the two film electrodes 14. Then the intermediate copperlayers 20 were formed over the zinc layers 18 by electroless plating.Then the outermost solder layers 22 were formed by electroplating a leadtin alloy over the copper layers 20.

We have thus completed the fabrication of monolithic, multilayeredceramic test capacitors 10, each constructed as in FIG. 1, in accordancewith the ceramic composition of Test No. 1 of Table 1. The compositionof the ceramic bodies 15 of the thus completed capacitors 10 provedsubstantially akin to that before sintering. It is therefore reasonedthat the sintered ceramic bodies 15 are of perovskite structures, withthe additives (1.0 mole percent B₂ O₃, 80.0 mole percent SiO₂, 3.8 molepercent BaO, 3.8 mole percent MgO, 3.8 mole percent ZnO, 3.8 molepercent SrO and 3.8 mole percent CaO) uniformly dispersed among thecrystal grains of the major ingredient.

As for the other ceramic compositions of Table 1, designated Tests Nos.2 through 98, we made similar capacitors through exactly the sameprocedure as that set forth in the foregoing in connection with the TestNo. 1 composition, except for the temperature of sintering in thereductive atmosphere, which will be referred to presently.

Then we tested all the capacitors of Tests Nos. 1-98 as to theirspecific dielectric constants, temperature coefficients of capacitance,Q factors, resistivities, and bending strengths. The following are themethods we employed for the measurement of these properties:

Specific Dielectric Constant

The capacitance of each test capacitor was first measured at atemperature of 20° C., a frequency of one megahertz, and an effectivealternating voltage of 0.5 volt. Then the specific dielectric constantwas computed from the measured value of capacitance, the area (25 squaremillimeters) of each of the overlapping parts of the two film electrodes14, and the thickness (0.02 millimeter) of that ceramic layer 12 whichintervenes between the film electrodes.

Temperature Coefficient of Capacitance

The capacitance C₈₅ at 85° C. and capacitance C₂₀ at 20° C. of each testcapacitor were first measured. Then the temperature coefficient TC ofcapacitance was computed by the equation

    TC=(C.sub.85 -C.sub.20)/C.sub.20 ×1/65×10.sup.6.

Q Factor

The Q factor was measured by a Q meter at a frequency of one megahertz,a temperature of 20° C., and an effective alternating voltage of 0.5volt.

Resistivity

Resistance across the pair of conductive terminations 16 of each testcapacitor 10 was measured after the application of a direct voltage of50 volts for one minute at a temperature of 20° C. Then the resistivitywas computed from the measured resistance value and the size of the testcapacitors.

Bending Strength

We employed the apparatus of FIG. 2 for the measurement of bendingstrength. The apparatus includes a dial gage 24 having a thrust rod 26to be loaded endwise against the center of each test capacitor 10. Thetest capacitor 10 was placed on a pair of parallel spaced ribs 28 formedon fixed supports 30. We read from the dial gage 24 the load that hasbeen exerted on the thrust rod 26 at the time of the breakage of thetest capacitor, and computed the bending strength (kg/cm²) by theequation:

    Bending strength=(3P·L)/(2b·d.sup.2)

where:

P=the maximum reading in kilograms of the dial gage 24;

L=the distance in centimeters between the pair of ribs 28;

b=the length in centimeters of each side of the test capacitor 10; and

d=the thickness in centimeters of the test capacitor 10.

The dimensions b and d of the test capacitor are subject to change fromspecimen to specimen. Typical values of b and d were 0.52 and 0.04centimeter, respectively.

Table 2 gives the results of the measurements by the above describedmethods, as well as the maximum temperatures at which the testcapacitors were sintered in the reductive atmosphere during theirmanufacture.

                                      TABLE 2                                     __________________________________________________________________________    Firing Temperature & Capacitor Characteristics                                        Capacitor Characteristics                                                           Temperature                                                        Firing                                                                             Specific                                                                            Coefficient of       Bending                                    Test                                                                             Temp.                                                                              Dielectric                                                                          Capacitance   Resistivity                                                                          Strength                                   No.                                                                              (°C.)                                                                       Constant                                                                            (ppm/°C.)                                                                      Q Factor                                                                            (megohm-cm)                                                                          (kg/cm.sup.2)                              __________________________________________________________________________     1 1160 59    -430    8700  2.4 × 10.sup.8                                                                 1680                                        2 "    60    -410    8500  2.6 × 10.sup.8                                                                 1700                                        3 "    62    -440    8900  2.3 × 10.sup.8                                                                 1670                                        4 "    60    -420    9000  2.4 × 10.sup.8                                                                 1690                                        5 "    58    -400    8700  2.5 × 10.sup.8                                                                 1720                                        6 "    61    -420    8400  2.7 × 10.sup.8                                                                 1730                                        7 1300 Not coherently bonded on firing.                                       8 "    "                                                                      9 "    "                                                                     10 "    "                                                                     11 "    "                                                                     12 "    "                                                                     13 1160 60    -400    8700  2.3 × 10.sup.8                                                                 1700                                       14 "    62    -410    8600  2.4 × 10.sup.8                                                                 1710                                       15 "    58    -450    9000  2.6 × 10.sup.8                                                                 1690                                       16 "    59    -420    8800  2.5 × 10.sup.8                                                                 1670                                       17 "    61    -430    8500  2.1 × 10.sup.8                                                                 "                                          18 "    62    -420    8400  2.7 × 10.sup.8                                                                 1730                                       19 "    59    -400    8800  2.6 × 10.sup.8                                                                 1700                                       20 "    58    -440    9000  2.5 × 10.sup.8                                                                 1680                                       21 "    61    -420    9100  2.7 × 10.sup.8                                                                 1690                                       22 "    60    -450    8800  2.6 × 10.sup.8                                                                 1660                                       23 "    63    -400    8600  2.2 × 10.sup.8                                                                 1700                                       24 "    59    -410    8700  2.3 × 10.sup.8                                                                 1710                                       25 "    58    -430    "     "      "                                          26 "    57    -400    8600  "      "                                          27 "    61    -450    8500  2.2 × 10.sup.8                                                                 1730                                       28 "    63    -420    8800  2.6 × 10.sup.8                                                                 1670                                       29 "    62    -410    9000  2.7 × 10.sup.8                                                                 1650                                       30 "    60    -400    8700  2.6 × 10.sup.8                                                                 1660                                       31 "    59    -420    8800  2.3 × 10.sup.8                                                                 1700                                       32 "    61    -440    9000  2.5 × 10.sup.8                                                                 1710                                       33 1170 43    -210    8700  6.9 × 10.sup.7                                                                 1400                                       34 1160 46    -220    8800  1.0 × 10.sup.8                                                                 1500                                       35 "    48    -240    "     1.9 × 10.sup.8                                                                 1550                                       36 "    47    -230    8700  2.4 × 10.sup.8                                                                 1600                                       37 1170 46    "       8600  2.0 × 10.sup.8                                                                 1530                                       38 1180 41    -200    8200  9.0 × 10.sup.7                                                                 1300                                       39 1170 42    -190    7900  7.0 × 10.sup.7                                                                 1330                                       40 1160 46    -210    8500  1.3 × 10.sup.8                                                                 1520                                       41 1150 47    -220    8600  1.7 × 10.sup.8                                                                 1590                                       42 "    46    -230    8500  2.0 × 10.sup.8                                                                 1570                                       43 1160 45    -210    8400  1.9 × 10.sup.8                                                                 1510                                       44 1170 42    "       8100  9.7 × 10.sup.7                                                                 1290                                       45 "    40    -200    8500  7.3 × 10.sup.7                                                                 1380                                       46 1160 44    -210    8700  1.6 × 10.sup.8                                                                 1520                                       47 1150 47    "       9000  2.0 × 10.sup.8                                                                 1570                                       48 1140 "     -220    8900  3.0 × 10.sup.8                                                                 1600                                       49 1160 46    -230    8800  1.9 × 10.sup.8                                                                 1550                                       50 1170 44    -220    8600  8.3 × 10.sup.7                                                                 1410                                       51 1180 43     -35    8100  9.0 × 10.sup.7                                                                 1300                                       52 1150 42     -40    8300  1.2 × 10.sup.8                                                                 1520                                       53 1140 40     -50    8400  2.9 × 10.sup.8                                                                 1600                                       54 1130 42     -40    8300  3.3 × 10.sup.8                                                                 1610                                       55 "    44     -30    8100  2.8 × 10.sup.8                                                                 1580                                       56 1190 46     -20    7900  1.0 × 10.sup.8                                                                 1520                                       57 1300 Not coherently bonded on firing.                                      58 1160 90    -840    8100  8.0 × 10.sup.7                                                                 1260                                       59 1140 85    -870    8000  1.3 × 10.sup.8                                                                 1500                                       60 1130 87    -840    8200  2.2 × 10.sup.8                                                                 1590                                       61 1150 91    -800    8300  2.6 × 10.sup.8                                                                 1600                                       62 1170 96    -780    8000  2.1 × 10.sup.8                                                                 1530                                       63 1200 99    -760    7400  1.3 × 10.sup.7                                                                 1390                                       64 1400 35     +45    7700  3.8 × 10.sup.8                                                                 1520                                       65 1130 36      0     8000  3.7 × 10.sup.8                                                                 1540                                       66 1120 46    -190    8100  3.5 × 10.sup.8                                                                 1560                                       67 1110 75    -720    8600  3.4 × 10.sup.8                                                                 1600                                       68 1120 134   -1000   8800  3.1 × 10.sup.8                                                                 "                                          69 "    152   -1430   8900  2.7 × 10.sup.8                                                                 1590                                       70 1180 41     -50    8200  7.0 × 10.sup.7                                                                 1300                                       71 1160 43     -40    8400  1.3 × 10.sup.8                                                                 1440                                       72 1140 "     "       8300  2.5 × 10.sup.8                                                                 1600                                       73 1130 41     -30    7900  2.0 × 10.sup.8                                                                 1580                                       74 1120 38     -20    7000  1.2 × 10.sup.8                                                                 1540                                       75 1110 33     -10    3000  8.0 × 10.sup.7                                                                 1400                                        76                                                                              1300 Not coherently bonded on firing.                                      77 1190 88    -550    7700  1.2 × 10.sup.8                                                                 1520                                       78 1160 87    -570    8000  1.7 × 10.sup.8                                                                 1600                                       79 1150 85    -590    8500  2.3 × 10.sup.8                                                                 1630                                       80 "    83    -610    9000  2.4 × 10.sup.8                                                                 1640                                       81 1170 80    -630    8900  2.3 × 10.sup.8                                                                 1620                                       82 1190 78    -650    8800  2.4 × 10.sup.8                                                                 1580                                       83 1300 Not coherently bonded on firing.                                      84 "    "                                                                     85 1180 88    -790    9500  1.9 × 10.sup.8                                                                 1580                                       86 1150 87    -750    9100  2.4 × 10.sup.8                                                                 1600                                       87 1100 79    -660    7900  "      1530                                       88 1070 74    -610    5900  2.0 × 10.sup.8                                                                 1500                                       89 1040 65    -590    2900  9.3 × 10.sup.7                                                                 1190                                       90 1140 56    -340    8000  1.6 × 10.sup.8                                                                 1520                                       91 1150 55    -340    8200  3.7 × 10.sup.8                                                                 1590                                       92 1160 54    -330    7800  3.5 ×  10.sup.8                                                                1620                                       93 1170 51    -300    7600  2.7 × 10.sup.8                                                                 1560                                       94 1190 48    -280    6300  5.0 × 10.sup.7                                                                 1400                                       95 1160 250   -720    9700  1.7 × 10.sup.7                                                                 1190                                       96 1120 133   -1000   8900  3.4 × 10.sup.8                                                                 1580                                       97 1100 37     -45    8300  2.8 × 10.sup.7                                                                 1310                                       98 "    38     -40    8400  5.0 × 10.sup.8                                                                 1600                                       __________________________________________________________________________

It will be noted from Table 2 that the specific dielectric constants ofthe Test No. 1 capacitors, for instance, averaged 59, their temperaturecoefficients of capacitance -430 ppm per degree C., their Q factors8700, their resistivities 2.4×10⁸ megohm-centimeters, and their bendingstrengths 1680 kilograms per square centimeter. The temperaturecoefficients of the capacitances of the test capacitors were practicallyconstant in the normal range of their operating temperatures.

It will further be observed from Table 2 that the dielectric bodies ofTests Nos. 7-12, 57, 76, 83 and 84 were not coherently bonded on firingat temperatures as high as 1300° C. in the reductive atmosphere. Thecorresponding ceramic compositions of Table 1 fall outside the scope ofour invention. The dielectric bodies of all the other Tests could besintered to maturity at temperatures less than 1200° C.

Before proceeding further with the examination of the results of Table 2we will determine the acceptable criteria of the five electrical andmechanical properties in question for the ceramic capacitors provided byour invention. These criteria are:

Specific dielectric constant:

From 35 to 135.

Temperature coefficient of capacitance:

From -1000 to +45 ppm per degree C.

Q factor:

Not less than 5000.

Resistivity:

Not less than 1×10⁸ megohm-cm.

Bending strenth:

Not less than 1500 kg/cm².

A reconsideration of Table 2 in light of the above established criteriaof favorable electrical and mechanical characteristics will reveal thatthe capacitors of Tests Nos. 33, 38, 39, 44, 45, 50, 51, 58, 63, 69, 70,71, 75, 89, 94, 95 and 97 do not meet these criteria. Accordingly, thecorresponding ceramic compositions of Table 1 also fall outside thescope of our invention. All the test capacitors but those of Tests Nos.7-12, 33, 38, 39, 44, 45, 50, 51, 57, 58, 63, 69, 70, 71, 75, 76, 83,84, 89, 94, 95 and 97 satisfy the criteria, so that their ceramiccompositions are in accord with our invention.

Now, let us study the ceramic compositions of Table 1 and thecorresponding capacitor characteristics, as well as the sinteringtemperatures, of Table 2 in more detail. The ceramic composition of TestNo. 84 contained no additive specified by our invention. The dielectricbodies formulated accordingly were not coherently bonded on firing at atemperature as high as 1300° C. Consider the ceramic composition of TestNo. 85 for comparison. They contained 0.2 part by weight of theadditives with respect to 100 parts by weight of the major ingredient.Even though the firing temperature was as low as 1180° C., the resultingtest capacitors possessed all the desired characteristics. We set,therefore, the lower limit of the possible proportions of the additivemixture at 0.2 part by weight with respect to 100 parts by weight of themajor ingredient.

The Test No. 89 ceramic composition contained as much as 12 parts byweight of the additives with respect to 100 parts by weight of the majoringredient. The resulting Test No. 89 capacitors had a Q factor of 2900,a resistivity of 9.3×10⁷ megohm-cm, and a bending strength of 1190kg/cm, which are all far less than the above established criteria. Whenthe proportion of the additive mixture was reduced to 10 parts byweight, as in Test No. 88, the resulting capacitors had all the desiredcharacteristics. Therefore, we set the upper limit of the possibleproportions of the additive mixture at 10 parts by weight with respectto 100 parts by weight of the major ingredient.

As for the major ingredient, we tested various values for the subscriptsv, w, x, y and k of the general formula in order to determine desirableranges of such values. First of all, the value of v was set at zero inTests Nos. 33, 39 and 45 and at 0.995 in Tests Nos. 38, 44 and 50. Inthe resulting capacitors the resistivities and bending strengths fellshort of the criteria. All the desired characteristics could be obtainedwhen the value of v was set at 0.005 as in Test No. 40, at 0.980 as inTest No. 37, and at various values in between. Thus the desired range ofvalues of v is between 0.005 and 0.980.

The value of w was set at 0 in Tests Nos. 51, 58, 70, 95 and 97. Theresulting capacitors were unsatisfactory in both resistivity and bendingstrength. Desired degrees of resistivity and bending strength could notbe obtained, either, when the value of w was made as high as 0.060 as inTests Nos. 57 and 63 or 0.055 as in Test No. 94. The desiredcharacteristics were all realized when the value of w was set at 0.001as in Test No. 59 and at 0.050 as in Tests No. 56 and 62. The acceptablerange of values of w is therefore from 0.001 to 0.050.

The value of 0.55 chosen for x in Test No. 69 was too high because theresulting capacitors had a temperature coefficient of only -1430ppm/°C., considerably less than the criterion of -1000 ppm/°C. When thevalue of x was set in the range of 0.00-0.50 as in Tests Nos. 64-68, thetemperature coefficients of the resulting capacitors fell in the targetrange of -1000-+45 ppm/°C. Thus the desired range of values of x is from0.00 to 0.50. It should be noted that the desired characteristics areobtainable if the value of x is zero as in Test No. 64, that is, if themajor ingredient contained no titanium.

The value of y was set at zero in Test No. 71, and the resultingcapacitors had a bending strength of only 1440, less than the criterionof 1500 kg/cm². As evidenced by Test No. 72, a bending strength of ashigh as 1600 kg/cm² was obtained when the value of y was set at 0.005.However, when the value of y was increased to 0.110 as in Test No. 75,the resulting capacitors were unsatisfactory in Q factor, resistivityand bending strength. Satisfactory characteristics resulted when thevalue of y was decreased to 0.100 as in Test No. 74. Accordingly, thedesired range of values of y is from 0.005 to 0.100.

When the value of k was set at 0.79 as in Test No. 76 and at 1.26 as inTest No. 83, the resulting dielectric bodies were not coherently bondedon firing at a temperature of as high as 1300° C. Coherently bondedceramic bodies were obtained, and the capacitor characteristics weresatisfactory, when the value of k was set in the range of 0.80-1.25 asin Tests Nos. 77-82. The desired range of values of k is therefore from0.80 to 1.25.

We included in these Tests some closest prior art ceramic compositionsin order to clearly illustrate the advantages of our present inventionover such prior art.

Test No. 70 represents one prior art ceramic composition whose majoringredient is:

    (CaO).sub.1.03 (Zr.sub.0.95 Ti.sub.0.05)O.sub.2.

Test No. 95 represents another prior art ceramic composition whose majoringredient is:

    (Sr.sub.0.62 Ca.sub.0.38 O)(Zr.sub.0.05 Ti.sub.0.95)O.sub.2.

Test No. 97 represents still another prior art ceramic composition whosemajor ingredient is:

    (Sr.sub.1.00 O).sub.1.00 (Zr.sub.0.95 Ti.sub.0.05)O.sub.2.

A comparison of the characteristics of the prior art ceramic capacitorsof these Tests with those of the inventive capacitors of, for example,Tests Nos. 72-74, 96 and 98 will reveal marked improvements inresistivity and bending strength in particular, obviously by reason ofthe additional inclusion of Ba, Mg and Si in the major ingredient inaccordance with our invention.

We have ascertained from the results of Table 2 that the acceptablerange of the relative proportions of B₂ O₃, SiO₂ and MO, the additivesof the ceramic compositions in accordance with our invention, can bedefinitely stated in reference to the ternary diagram of FIG. 3.

The point A in the ternary diagram indicates the Test No. 1 additivecomposition of one mole percent B₂ O₃, 80 mole percent SiO₂ and 19 molepercent MO. The point B indicates the Test No. 2 additive composition ofone mole percent B₂ O₃, 39 mole percent SiO₂ and 60 mole percent MO. Thepoint C indicates the Test No. 3 additive composition of 29 mole percentB₂ O₃, one mole percent SiO₂ and 70 mole percent MO. The point Dindicates the Test No. 4 additive composition of 90 mole percent B₂ O₃,one mole percent SiO₂ and nine mole percent MO. The point E indicatesthe Test No. 5 additive composition of 90 mole percent B₂ O₃, nine molepercent SiO₂ and one mole percent MO. The point F indicates the Test No.6 additive composition of 19 mole percent B₂ O₃, 80 mole percent SiO₂,and one mole percent MO.

The relative proportions of the additives B₂ O₃, SiO₂ and MO of theceramic compositions in accordance with our invention are within theregion bounded by the lines sequentially connecting the above statedpoints A, B, C, D, E and F in the ternary diagram of FIG. 3.

Tables 1 and 2 prove that the additive compositions within the abovedefined region makes possible the provision of capacitors of the desiredelectrical and mechanical characteristics. The additive compositions ofTests Nos. 7-12 all fall outside that region, and the correspondingdielectric bodies were not coherently bonded on firing at a temperatureof as high as 1300° C. The above specified acceptable range of therelative proportions of the additives holds true regardless of whetheronly one of BaO, MgO, ZnO, SrO and CaO is employed as MO, as in TestsNos. 22-26, or two or more or all of them are employed in suitablerelative proportions as in other Tests.

Although we have disclosed our invention in terms of specific Examplesthereof, we understand that our invention is not to be limited by theexact details of such disclosure but admits of a variety ofmodifications or alterations within the usual knowledge of theceramists, chemists or electricians without departing from the scope ofthe invention. The following, then, is a brief list of such possiblemodifications or alterations:

1. The low temperature sinterable ceramic compositions of our inventionmay include various additives other than those disclosed herein. Anexample is a mineralizer such as manganese dioxide. Used in a proportion(preferably from 0.05 to 0.10 percent by weight) not adversely affectingthe desired characteristics of the resulting capacitors, such amineralizer will lead to the improvement of sinterability.

2. The start materials of the ceramic compositions in accordance withour invention may be substances such as oxides or hydroxides other thanthose employed in the foregoing Examples.

3. The temperature of the oxidizing heat treatment need not necessarilybe 600° C. but can be variously determined in a range (from 500° to1000° C., for the best results) not exceeding the temperature of thepreceding sintering in a nonoxidative atmosphere, the oxidizingtemperature being dependent upon factors such as the particular basemetal electrode material in use and the degree of oxidation required forthe ceramic material.

4. The temperature of cosintering in a nonoxidative atmosphere may alsobe changed in consideration of the particular electrode material in use.We recommend a range of 1050° to 1200° C. if the electrode material isnickel, as we have ascertained from experiment that little or noflocculation of the nickel particles takes place in that temperaturerange.

5. The dielectric bodies and electrodes may be cosintered in a neutral,instead of reductive, atmosphere.

6. The ceramic compositions disclosed herein may be employed forcapacitors other than those of the multilayered configuration.

What we claim is:
 1. A low temperature sintered solid dielectriccapacitor comprising a dielectric ceramic body and at least twoelectrodes in contact therewith, the dielectric ceramic body consistingessentially of:(a) 100 parts by weight of a major ingredient expressedby the formula,

    (Ba.sub.1-v-w Me.sub.v Mg.sub.w O).sub.k (Zr.sub.1-x-y Ti.sub.x Si.sub.y)O.sub.2,

whereMe is at least either of strontium and calcium; v is a numeral inthe range of 0.005 to 0.980 inclusive; w is a numeral in the range of0.001 to 0.050 inclusive; x is a numeral in the range of 0.00 to 0.50inclusive; y is a numeral in the range of 0.005 to 0.100 inclusive; andk is a numeral in the range of 0.80 to 1.25 inclusive; and (b) from 0.2to 10.0 parts by weight of an additive mixture of boric oxide, silicondioxide and at least one metal oxide selected from the group consistingof barium oxide, magnesium oxide, zinc oxide, strontium oxide andcalcium oxide, the relative proportions of boric oxide, silicon dioxideand at least one selected metal oxide constituting the additive mixturebeing in that region of the ternary diagram of FIG. 3 attached heretowhich is bounded by lines sequentially connecting:the point A where theadditive mixture consists of one mole percent boric oxide, 80 molepercent silicon dioxide, and 19 mole percent metal oxide; the point Bwhere the additive mixture consists of one mole percent boric oxide, 39mole percent silicon dioxide, and 60 mole percent metal oxide; the pointC where the additive mixture consists of 29 mole percent boric oxide,one mole percent silicon dioxide, and 70 mole percent metal oxide; thepoint D where the additive mixture consists of 90 mole percent boricoxide, one mole percent silicon dioxide, and nine mole percent metaloxide; the point E where the additive mixture consists of 90 molepercent boric oxide, nine mole percent silicon dioxide, and one molepercent metal oxide; and the point F where the additive mixture consistsof 19 mole percent boric oxide, 80 mole percent silicon dioxide, and onemole percent metal oxide.
 2. A low temperature sintered solid dielectriccapacitor as set forth in claim 1, wherein the electrodes are buried inthe dielectric ceramic body.
 3. A low temperature sinitered soliddielectric capacitor as set forth in claim 1, wherein the electrodes areof a base metal.
 4. A low temperature sintered solid dielectriccapacitor as set forth in claim 3, wherein the base metal is nickel. 5.A process for the manufacture of a low temperature sintered soliddielectric capacitor, which process comprises:(a) providing a mixtureof:100 parts by weight of a major ingredient, in finely divided form,that is expressed by the formula,

    (Ba.sub.1-v-w Me.sub.v Mg.sub.w O).sub.k (Zr.sub.1-x-y Ti.sub.x Si.sub.y)0.sub.2,

whereMe is at least either of strontium and calcium; v is a numeral inthe range of 0.005 to 0.980 inclusive; w is a numeral in the range of0.001 to 0.050 inclusive; x is a numeral in the range of 0.00 to 0.50inclusive; y is a numeral in the range of 0.005 to 0.100 inclusive; andk is a numeral in the range of 0.80 to 1.25 inclusive; and from 0.2 to10.0 parts by weight of an additive mixture, in finely divided form, ofboric oxide, silicon dioxide and at least one metal oxide selected fromthe group consisting of barium oxide, magnesium oxide, zinc oxide,strontium oxide and calcium oxide, the relative proportions of boricoxide, silicon dioxide and at least one selected metal oxideconstituting the additive mixture being in that region of the ternarydiagram of FIG. 3 attached hereto which is bounded by lines sequentiallyconnecting:the point A where the additive mixture consists of one molepercent boric oxide, 80 mole percent silicon dioxide, and 19 molepercent metal oxide; the point B where the additive mixture consists ofone mole percent boric oxide, 39 mole percent silicon dioxide, and 60mole percent metal oxide; the point C where the additive mixtureconsists of 29 mole percent boric oxide, one mole percent silicondioxide, and 70 mole percent metal oxide; the point D where the additivemixture consists of 90 mole percent boric oxide, one mole percentsilicon dioxide, and nine mole percent metal oxide; the point E wherethe additive mixture consists of 90 mole percent boric oxide, nine molepercent silicon dioxide, and one mole percent metal oxide; and the pointF where the additive mixture consists of 19 mole percent boric oxide, 80mole percent silicon dioxide, and one mole percent metal oxide; (b)molding the mixture into desired shape and size, the molding having atleast two electrode portions of an electroconductive material; (c)cosintering the molding and the electrode portions to maturity in anonoxidative atmosphere; and (d) reheating the cosintered molding andelectrode portions in an oxidative atmosphere.
 6. A process for themanufacture of a low temperature sintered solid dielectric capacitor asset forth in claim 5, wherein the electrode portions are formed on themolding by coating the same with an electroconductive paste composedprincipally of a base metal.
 7. A process for the manufacture of a lowtemperature sintered solid dielectric capacitor as set forth in claim 6,wherein the base metal is nickel.
 8. A process for the manufacture of alow temperature sintered solid dielectric capacitor as set forth inclaim 5, wherein the molding and the electrode portions are cosinteredto maturity in a temperature range of 1050° to 1200° C.
 9. A process forthe manufacture of a low temperature sintered solid dielectric capacitoras set forth in claim 5, wherein the cosintered molding and electrodeportions are reheated in a temperature range of 500° to 1000° C.